Status of "Bulletin 17B" Flood-Frequency Guidelines

In Reply Refer To:                                              April 14, 1988
WGS-Mail Stop 415


Subject:  Status of "Bulletin 17B" Flood-Frequency Guidelines

The Hydrology Subcommittee of the Interagency Advisory Committee for Water
Data has completed a study of whether its flood-frequency guidelines
(Bulletin 17B) are meeting the needs of Federal agencies and whether the
guidelines should be revised or extended.  As part of this study, a question-
naire was distributed (Surface Water Branch Technical Memorandum 85.05, dated
February 14, 1985) to identify problems and solicit suggestions for improve-
ment of the Bulletin 17B methodology.  A copy of the study team's report to
the subcommittee is attached.

The study found that a number of problems are sometimes encountered in using
Bulletin 17B and recommended that a series of pamphlets be prepared to provide
additional guidance in solving these problems.  The Hydrology Subcommittee
agreed to form a work group to follow up on this recommendation.

The main conclusions of the study, however, are that on the whole the guide-
lines prescribe technically sound procedures, that no substantial problems
within the scope of the guidelines have been identified that cannot be handled
by means included in the guidelines, and that no breakthroughs in statistical
practice have occurred to provide feasible, substantial, and clearly superior
technical alternatives to the Bulletin 17B methodology.  Therefore the
Hydrology Subcommittee has decided that replacement or revision of Bulletin
17B is not warranted at this time.

U.S. Geological Survey (USGS) offices that perform flood-frequency analyses
should continue to follow the Bulletin 17B guidelines until further notice.
These guidelines were distributed by Surface Water Branch Technical Memorandum
82.04, dated October 16, 1981.  It should be noted that the guidelines include
provisions for the properly documented use of alternative methodologies where
necessary.  Computer program J407, described in the WATSTORE Users Guide,
volume 4, chapter I.C, continues to be the USGS implementation of the Bulletin.
This program also has been modified to run on the Prime computer, and it is
expected to be included in the next release of the ANNIE/WDMS system (see
Office of Surface Water Technical Memorandum 87.08 dated, April 21, 1987).

                                    Charles W. Boning
                                    Acting Chief, Office of Surface Water


Distribution:  FO-LS; SL